This invention relates to rechargeable zinc ion batteries.
Due to the fast pace of expansion of human activity and exhaustion of fuel oil, high energy density electrochemically rechargeable energy storage systems are the key to the future realization of a myriad of next generation applications ranging from biomedical to electric vehicles. The single-ion battery is one of the most widely used rechargeable systems. It utilizes at least one intercalation electrode with the guest cations, univalent or bivalent cations, as the charge storage medium. Two single-ion battery technologies, for example, nickel metal hybrids (NiMeH) and lithium ion, have been commercialized for mass applications. NiMeH batteries utilize the reversible intercalation of a H+ guest cation into NiOOH and alloying reactions with rare earth electrodes. The rocking chair Li-ion battery utilizes intercalation reactions of Li+ ions into oxides positive electrodes or carbon-based negative electrodes. It is certain that it is significantly important to invent new single ion batteries from scientific and industrial points of view.
The fundamentals of manganese dioxide chemistry for energy storage continue to be of widespread interest. Since 1865, zinc-manganese dioxide battery chemistry has been proposed and a kind of primary zinc-manganese dioxide battery has been built up. This primary battery contains γ-MnO2 cathode and a zinc anode using zinc chloride and ammonium chloride solutions as the electrolyte.
The discharge process of positive γ- MnO2 cathode in such cells is based on two electron steps. The first electron process is described as follow:MnO2+NH4++e→MnOOH+NH3↑  (1)orMnO2+H++e→MnOOH   (2)
If the electrode continues to discharge, MnOOH is further reduced at the second step:MnOOH+H++e−→MnO2+Mn2++2H2O   (3)
During the two electron steps of positive γ-MnO2 cathode, anodic zinc will be electrochemically dissolved.
In the middle of 20th century, an alkaline manganese dioxide-zinc battery has been built up based on alkaline electrolytes. The first electron process of positive γ-MnO2 cathode in such alkaline cells is following:MnO2+H2O+e→MnOOH+OH−  (4)
In the second electron process, the reaction is:MnOOH+H2O→Mn(OH)2+OH−  (5)
At the same process, the chemical reaction on zinc anode is:Zn+4OH−→Zn[(OH)4]2−+2e   (6)
In such alkaline batteries, the electrolyte is not consumed during discharge, which increases the energy storage capacity. Additionally, the high alkaline conductivity can improve battery performance in the high-power domain. Capacity, cost, power, and safety factors have led to the annual global use of approximately 60 billions alkaline manganese dioxide-zinc batteries [Besenhard, J. O., Handbook of Battery Materials Wiley-VCH, 1999].
In 1977, Kordesch had firstly developed the rechargeable alkaline manganese dioxide zinc (RAM) batteries, in which the discharge of positive MnO2 was limited to a depth of one electron per mole of MnO2 by controlling the anode mass. The total reaction of the cell could be expressed as below:2MnO2+Zn+H2O⇄2MnOOH+Zn(OH)2   (7)
Although this rechargeable alkaline manganese dioxide zinc battery needs more procedures or special components than do the primary Zn/MnO2 batteries resulting in the enhancement of the cost as well as sacrificing the capacity, however, the RAM batteries still share more than half of the alkaline battery market due to its recharge ability in USA.
Unfortunately, some critical issues of these RAM batteries limit it to be used in a broader scope. Firstly, they tend to exhibit a sharp decline in discharge capacity with cycling, and reducing the amount of zinc available in the cell only accelerates this situation. Secondly, the coulombic efficiency of such cells is relatively slow. And it also generally acknowledged that it is difficult to industrialize such batteries capable of high-rate charging or discharging [Shen Y. & Kordesch K., The mechanism of capacity fade of rechargeable alkaline manganese dioxide zinc cells. J Power Sources 2000, 87, 162]. As the quantity and variety of the electric devices blossomed in recent years or will be in the future, it is always desired to develop new batteries with the improved performance in terms of power, capacity, coulombic efficiency, cycle life as well as cost to meet the continuous-enhanced demands.